The present invention relates to a process for the production of highly effective surface treating agents. The surface treating agents produced in accordance with this invention comprise mixtures containing fluorinated pyromellitate nuclei. The pyromellitate nuclei contain fluorinated ester moieties which impart water and oil repelling characteristics to various fibers.
U.S. Pat. No. 4,209,610 (Mares et al., 1980) discloses fluorinated pyromellitates useful as surface modifiers for polyamides and polyesters. One preferred group of compounds in that patent are those of the formula: ##STR1## wherein A is a fluorinated ester such as CF.sub.3 (CF.sub.2).sub.p R'O(O)C-- and wherein B is HOCH(CH.sub.2 Cl)CH.sub.2 O(O)C--; wherein R' is ethylene and p is a mixture of integers such as 3, 5, 7, 9 and 11 for different chains. Such products are formed by the reaction of pyromellitic dianhydride with a fluorinated alcohol, and then the reaction of the product diacid/diester with epichlorohydrin. Specifically, the product is produced by reaction of two moles of fluorinated alcohol with each mole of pyromellitic dianhydride to form the diacid/diester. Each mole of the diacid/diester is then reacted with two moles of epichlorohydrin to produce the product. Because the oxirane may react at the one or two carbon, the product will normally contain minor amounts of material with B being HOCH.sub.2 CH(CH.sub.2 Cl)O(O)C-- (the product with a pendant primary alcohol) as well as major amounts of material with B being HOCH(CH.sub.2 Cl)CH.sub.2 O(O)C-- (the product with a pendant secondary alcohol). Other patents relating to the production of this product include U.S. Pat. No. 4,252,982 (Oxenrider 1981) wherein an ester solvent is used and U.S. Pat. No. 4,321,403 (Oxenrider et al., 1981) wherein N-methylpyrrolidone is used as solvent. Methods for applying the compound in aqueous emulsions to fibers are disclosed in U.S. Pat. Nos. 4,192,754 (Marshall et al., 1980), 4,134,839 (Marshall, 1979), 4,190,545 (Marshall et al., 1980), 4,193,880 (1980), 4,283,292 (Marshall, 1981) and 4,317,736 (Marshall, 1982).
My copending, commonly assigned application Ser. No. 380,188, now U.S. Pat. No. 4,446,306, describes a process for the production of pyromellitate oligomers useful as surface treating agents wherein a mole ratio of fluorinated alcohol to pyromellitic dianhydride of less than 2:1 is employed.
In a modification of copending, commonly assigned application Ser. No. 380,188, application Ser. No. 412,620, now U.S. Pat. No. 4,414,277, describes a simple two step process for the production of oligomeric surfactants. Initially, pyromellitic dianhydride is reacted with fluorinated alcohol with the mole ratio of pyromellitic dianhydride to fluorinated alcohol being about 2:1. Thereafter, the fluorinated pyromellitate compound is reacted with an oxirane compound in the presence of additional pyromellitic dianhydride to produce oligomeric mixtures.
The fluorinated pyromellitate containing mixtures of the present invention have extremely high resistance to soiling, and the soil resistant properties imparted to fibers by the compositions of this invention are retained by the fibers after numerous laundering cycles. Therefore, fibers treated with the fluorinated pyromellitate containing mixtures of the present invention will retain soil resistance properties for long periods of time in an environment where they are ultimately employed. Furthermore, as described in each of the above patents, an annealing step is employed after the application of the compound to the fiber. It is desirable to be able to lower the temperature of the annealing step, for energy savings, without impairing either the initial soil resistance or the retention of soil resistance after laundering. With the fluorinated pyromellitate containing mixtures of the present invention, the annealing step may be accomplished at temperatures as low as about 50.degree. C.
Also, some of the fluorinated surfactants of the present invention contain a lesser mole percent of fluorine than most of the compositions described by the above-referenced patents or pending patent applications. Since fluorinated alcohol from which the fluorine moiety is derived is somewhat expensive, any reduction in the amount of fluorinated alcohol that must be employed to produce a given amount of product results in a cost savings.